Topic summary
Light waves
Extracted from the Wikipedia article Light.
Wave theory
The wave theory predicted that light waves could interfere with each other like sound waves (as noted around 1800 by Thomas Young). Young showed by means of numerous diffraction experiments that light behaved as waves. He first publicly stated his "general law" of interference in January 1802, in his book A Syllabus of a Course of Lectures on Natural and Experimental Philosophy: